In the case of many doors, windows and other such elements provided with a rotatable handle, it is desirable to be able to selectively couple a part that can be turned or rotated by means of the handle to another part, or to disengage it therefrom. The other part may consist either of a similarly rotatable part or of a fixed part.
Where both of the parts are rotatable, it may be desirable in a disengaged state, for example, to allow the handle to be turned without affecting the other part and in a coupled state to allow a rotational movement of the handle to be transmitted to the other part. The other part may then consist, for example of a swivel pin, such as a handle shank, which is in turn capable of transmitting the rotational movement to a tumbler, a bolt, an espagnolette bolt, a lock or some other device for influencing the state of the door or the window. In the coupled position, operation therefore occurs in the normal way by means of the handle. In the disengaged position, on the other hand, the state of the door or window remains unaffected if the handle is turned. Such selective disengagement may be used, for example, as a child safeguard, in order to prevent an external door or a window being opened from the inside or in order to prevent damage to a lock or the like coupled to the handle if excessive forces are applied to the handle when the lock is in the locked position.
Where the second part consists of a fixed, non-rotatable part, the rotatable handle can be conventionally fixed or continuously coupled by means of a handle shank to a bolt, an espagnolette bolt, or a lock, for example, or some other device for influencing the state of the door or the window. Disengagement and coupling between the rotatable handle and the fixed part can then be used, in the disengaged position, to allow operation and, in the coupled position, to lock the handle and thereby prevent operation of the door or the window. The coupling between the handle and the fixed part can in this respect be said to constitute a lock. Such selective disengagement and coupling between the rotatable handle and the fixed part can be used as a child safeguard, for example, or in order to prevent unauthorized operation of a door or a window.
In both cases the disengagement and coupling between the rotatable handle and the other part can be achieved manually, for example by operating a mechanical button, a lock cylinder or the like. Recently, however, it has become increasingly more common to bring about such a disengagement and coupling by electromechanical means. This allows disengagement and/or coupling, for example, only if an authorized user has first entered a code via a keypad or entered an identification via an electronic card reader.